Hot desert environments

Where hot deserts are

A gets less than 250 mm of rain a year. Most lie between about 15° and 30° north and south of the equator: the Sahara, the Arabian Desert, the Thar Desert in India and Pakistan, and the deserts of central Australia.

At these latitudes, air that rose at the equator sinks. Sinking air warms and dries, so clouds rarely form: this is a belt of . Clear skies let the sun heat the ground strongly by day.

Key terms

The hot desert climate

A hot desert climate on the edge of the monsoon (data written for this app).

Hot: often over 40 °C on summer afternoons. Monthly averages are lower, because they include the nights.
Dry: this desert gets about 240 mm in a year, mostly in a few summer storms. Some years get much less.
with no clouds to trap heat, nights can be cold, even near freezing in winter.

Exam tip

Describe a climate graph with figures: the hottest and wettest months, the totals and the range.

Key terms

Soils and interdependence

Desert soils are thin, sandy or stony, and dry. With few plants, there is little dead matter, so they hold few nutrients. Water evaporating from the surface can leave salts behind.

The parts of the desert are :

the climate controls how much plants can grow;
plants give animals food, water and shade, and hold the soil together;
animals spread seeds and add nutrients in their droppings;
people graze goats and camels, collect firewood and farm, which affects all of these.

Because rain is scarce and growth is slow, a change to one part, such as , can quickly damage the rest.

Key terms

Plant adaptations

Desert plants are adapted to save water and survive long droughts:

Long tap roots reach water deep underground. The khejri tree of the Thar has roots many metres long.
Spreading shallow roots catch rain before it evaporates, as in cacti.
Spines instead of leaves lose less water and keep animals away; the stem does the photosynthesis.
Thick, waxy skin cuts water loss; cacti store water in swollen stems.
Seeds can lie dormant for years, then grow, flower and seed within weeks of rain.

Key terms

Animal adaptations and biodiversity

Camels store fat in their humps, can go days without drinking, and have wide feet for sand and long eyelashes against sandstorms.
Fennec foxes lose heat through large ears.
Many animals are : they shelter in burrows by day and come out in the cool of night.
The blackbuck and chinkara gazelle of the Thar get much of their water from the plants they eat.

is low compared with wetter places, but many species live nowhere else. It is under threat from , hunting, farming and climate change: the great Indian bustard of the Thar is critically endangered.

Key terms

Exam practice

Plan your own answer first, then open the model answers to see what each level looks like.

6 marks · about 6 minutes

Explain the interdependence of the climate, soils, plants, animals and people in a hot desert.

Explain means: Give the reasons why something happens, developing each point with "because" or "so".

Level 1 (Basic)· 2/6 marks (band 1–2)

Deserts are hot and dry. Plants and animals have to cope with this. People keep goats.

Why this level: Describes the parts of the desert but doesn't show how they depend on each other. To reach Level 2: explain the links, such as how climate controls plants, and how plants support animals.

Level 2 (Clear)· 4/6 marks (band 3–4)

In a hot desert, the low rainfall means few plants can grow. Plants provide animals with food and shade, and their roots hold the soil together. Animals spread seeds and add nutrients to the soil in their droppings. People graze goats on the plants.

Why this level: Clear links between several parts. To reach Level 3: develop the links further and show how a change to one part, such as overgrazing, affects the rest.

Level 3 (Detailed)· 6/6 marks (band 5–6)

In a hot desert, the very low rainfall controls how much plants can grow. The plants that survive give animals food, water and shade, and their roots hold the thin, sandy soil together. Animals spread seeds and add nutrients to the soil in their droppings, which helps more plants grow. People depend on all of these: they graze goats and camels on the plants and collect wood for fuel. Because plants grow so slowly, a change to one part can quickly damage the rest. For example, overgrazing removes plants, so the soil is no longer held together and is blown away by the wind, leaving even less for animals and people.

Why this level: Detailed, well-linked explanation of climate, soils, plants, animals and people, with a developed example of how one change spreads. This is Level 3.

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